The reduction of semiconductor device dimensions has increased the density of semiconductor circuitry to a point where interconnect line-to-line capacitance can impact the speed (due to propagation delay) and reliability (due to crosstalk noise) of semiconductor devices. Manufacturers are addressing this is by incorporating changes to semiconductor device fabrication processes. One such change includes converting interlayer dielectrics (ILDs) from silicon dioxide-based (SiO2-based) materials (i.e., conventional SiO2, which has a dielectric constant of approximately 3.9-4.2 and fluorinated silicon dioxide, which has a dielectric constant of approximately 3.5) to alternative low dielectric constant (low-k) materials. Decreasing the ILD's dielectric constant decreases line-to-line capacitance and its associated effects on device performance.
Carbon-doped oxides (CDOs) are one alternative being investigated to replace SiO2-based ILDs. FIG. 2 illustrates an example of a carbon-doped oxide molecular network 20. The network 20 includes atoms of silicon 22, oxygen 24, and hydrogen 26, as well as carbon-containing groups 28. CDO dielectrics such as this can be deposited by way of plasma enhanced chemical vapor deposition (PECVD) using precursors such as dimethyldimethoxysilane (DMDMOS), diethoxydimethylsilane (DEMS), and octamethylcyclotetrasiloxane (OMCTS).
In carbon-doped oxide networks 20, methyl groups 28 and hydrogen atoms 26 do not contribute to intermolecular network bonding. Voids that are produced as a result of this contribute to lowering the ILD's dielectric constant. The reduction in intermolecular network bond also reduces the ILD's modulus of elasticity (i.e., one measure of the ILD's mechanical strength). So, while CDO ILDs may have lower dielectric constants as compared to SiO2-based ILDs, they are also mechanically weaker (modulus of elasticity of CDO approximately equal to 15 GPa; modulus of elasticity of SiO2 approximately equal to 60-70 GPa).
Low modulus of elasticity materials are more susceptible to deformation or damage when subject to compressive, tensile, and sheer stresses. Inability to withstand these stresses during subsequent manufacturing processes, such as chemical mechanical planarization, die singulation, wafer probe, wire bond, die attach, etc., limits their attractiveness because expensive and time consuming process/retooling changes may be required in order to accommodate them.
It will be appreciated that for simplicity and clarity of illustration, elements in the drawings have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Where considered appropriate, reference numerals have been repeated among the drawings to indicate corresponding or analogous elements.